Light emitting device

ABSTRACT

A light emitting device having a plastic substrate is capable of preventing the substrate from deterioration with the transmission of oxygen or moisture content can be obtained. The light emitting device has light emitting elements formed between a lamination layer and an inorganic compound layer that transmits visual light, where the lamination layer is constructed of one unit or two or more units, and each unit is a laminated structure of a metal layer and an organic compound layer. Alternatively, the light emitting device has light emitting elements formed between a lamination layer and an inorganic compound layer that transmits visual light, where the lamination layer is constructed of one unit or two or more units, and each unit is a laminated structure of a metal layer and an organic compound layer, wherein the inorganic compound layer is formed so as to cover the end face of the lamination layer. In the present invention, the lamination layer is formed on the primary surface of the plastic substrate, so that a flexible substrate structure can be obtained while preventing the substrate from deterioration with the transmission of oxygen or moisture content.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a light emitting device using anorganic compound material as a luminescent material, and in particular,to the configuration of a light emitting device in which a plasticmaterial is used as a substrate.

2. Description of the Related art

Heretofore, a light emitting device utilizing a luminescence phenomenonwith electroluminescence (hereinafter, referred to as EL) has beeninvestigated so as to be applied as a means for forming image thatrepresents information such as characters and images. Among inorganiccompound materials, zinc sulfide has been known as a typical luminescentmaterial (EL material) that generates EL. On the other hand, amongorganic compound materials, an aluminum tris (8-hydroxyquinoline) (Alq3)complex has been known as a typical EL material.

The light emitting element using such an EL material has a comparativelysimple structure and contains a luminescent material included in acoating film of several hundreds nanometers between a pair ofelectrodes. From the view point of diversity of the material, it isconsidered that the luminescent material containing the organic compoundmaterial is superior to one containing the inorganic compound material.Initially, it was concerned that the life of light emission was short.In recent years, however, an organic compound material having abrightness half life of over 10,000 hours has been developed.

The light emitting device adapted to various kinds of applications suchas a lighting means or a displaying means by the use of a light emittingelement obtains additional advantages of weight saving, low-profiling,resistance to breakage, flexibility, and so on. Therefore, the values asa charming product can be expected.

However, there is a problem in that the plastic material has low heatresistance properties compared a glass material. Even though such aproblem can be overcame by decreasing the process temperature, it isdifficult to implement a light emitting device having such a plasticmaterial as a substrate because the plastic material has the property ofallowing the transmission of oxygen and moisture content, and theproperty of occluding oxygen and moisture content and releasing themagain depending on the temperature. In other words, there is a problemthat the organic compound material or which is one of the structuralcomponents of the light emitting device or an anode material using thealkali metal can be influenced and the light-emitting function thereofcan be decreased.

For solving such a problem, for example, the following methods aredisclosed. That is, a method of using a material having high moisturebarrier properties such as a fluorine film as a plastic material, amethod of forming a thin film layer containing one or two or more ofmaterials selected from metal fluorides and magnesium oxides essentiallycontaining silicon oxide as disclosed in JP8-167475, a method of forminga gas-barrier layer by laminating inorganic nitride and inorganic oxideas disclosed in JP8-68990. In the U.S. Pat. No. 6,268,695, there isdisclosed a laminate structure as a barrier layer in which polymerlayers and ceramic layers are laminated one after another.

However, the fluorine film is expensive and a sufficient thickness ofthe film is required for attaining sufficient gas-barrier properties. Asa result, there is a problem of lowering transmissivity. In addition,the coating film made of the inorganic compound such as nitride or oxidehas a high internal stress, so that the plastic substrate can bedeformed when the coating film is thickened. On the other hand, if thecoating film is thinned, a sufficient gas barrier property cannot beobtained and a pin hole or the like tends to be caused. Therefore, thereis a problem in that a sufficient effect as a sealing material cannot beobtained. Furthermore a fine film made of silicon oxide or siliconcannot be obtained if the material is not heated to the heat-resistancetemperature or more of the plastic material. On the other hand, when thetemperature decreases, the coating film becomes coarse and the gasbarrier property decreases. These features are mutually contradictory,so that the plastic substrate cannot be coated with a fine film.

Furthermore, silica, alumina, titanium oxide, indium oxide, tin oxide ,indium tine oxide (ITO, indium oxide mixed with tin oxide), aluminumnitride, silicon nitride, or the like selected as a ceramic layer hasbrittleness, so that it may be not always preferable to use a flexibleplastic material as a substrate. In addition, it becomes possible toendure some degree of bending if the ceramic layer is formed as a thinfilm. In this case, however, the probability of generating a pin holeincreases and so on, resulting in a decrease in gas barrier property.

SUMMARY OF THE INVENTION

In consideration of the above circumstances, an object of the presentinvention is to provide a light emitting device using a plastic materialas a substrate, which is capable of preventing the substrate fromdeterioration with the transmission of oxygen or moisture content.

For solving the above problems, a lamination layer is formed on theprinciple surface of a substrate made of a plastic material to preventthe substrate from deterioration with the transmission of oxygen ormoisture content, and functional elements including light emittingelements are formed on the lamination layer. Furthermore, an inorganiccompound layer having gas barrier properties is also formed on thesefunctional elements and the inorganic compound layer and the surface orend surface of the lamination layer are laminated together on theoutside of the functional elements or functional element groups to forma sealed sealing structure.

The plastic material may be selected from polyether sulphone,polyallylate, polyimide, polyamide, acryl resin, epoxy resin,polyethylene terephthalate, polyethylene naphthalate, and polycarbonate.In addition, other plastic materials well known in the art may be usedas far as they have some degrees of heat resistance and mechanicalstrength enough to form functional elements.

The lamination layer may be a laminate of a metal layer and an organiccompound layer. As a metal material, aluminum is particularly preferablebecause of its comparatively soft and flexible structure. Other metalmaterials usable in the present invention may include chromium,titanium, tungsten, stainless steel alloy, and so on. In this case,there is a need of forming the film of 5 nm or less in thickness andmaking the film difficult to be cracked when the plastic substrate isbent. The organic compound layer is provided for relaxing the stress,and is selected from heat-curing or photo-curing organic resinmaterials, typically a polyimide resin or an acryl resin.

The light emitting device of the present invention having the aboverequirements comprises light emitting elements formed between alamination layer and an inorganic compound layer that transmits visuallight, where the lamination layer is constructed of one unit or two ormore units, and each unit is a laminated structure of a metal layer andan organic compound layer. Alternatively, the light emitting devicecomprises: light emitting elements formed between a lamination layer andan inorganic compound layer that transmits visual light, where thelamination layer is constructed of one unit or two or more units, andeach unit is a laminated structure of a metal layer and an organiccompound layer, wherein the inorganic compound layer is formed so as tocover the end face of the lamination layer.

In such a configuration of the present invention, a thin film transistor(hereinafter, referred to as TFT) connected to the light emittingelement may be formed in matrix form to provide a pixel portion. Thepixel portion may be arranged between the lamination layer and theinorganic compound layer.

A light emitting device of the present invention comprises a pixelportion having light emitting elements in which a luminescent layercontaining a luminescent material made of an organic compound between afirst electrode and a second electrode connected to a plurality ofpixels and extended in one direction, and wiring connected to the firstelectrode and extended in the direction intersecting the one direction,wherein the pixel portion is formed between a lamination layer and aninorganic compound layer that transmits visual light, where thelamination layer is constructed of one unit or more units, and each unitis a laminated structure of a metal layer and an organic compound layer.The inorganic compound layer may be formed so as to cover the end faceof the lamination layer.

An intermediate layer may be formed between the lamination layer and thelight emitting element, between the lamination layer and the TFT, orbetween the lamination layer and the pixel portion.

In the configuration of the lamination layer, the metal layer may beformed of aluminum or aluminum alloy, and the organic compound layer maybe formed of a heat-curable or photo-curable resin material.

In a typical mode of the light emitting element used in the presentinvention, a layer containing the above luminescent material is placedbetween a pair of electrodes divided into a cathode and an anodedepending on their polarities. The layers can be functionallyrepresented by a luminescent layer, a hole-injection layer, aelectron-injection layer, a hole transport layer, a electron transportlayer, and so on. As an extremely simple configuration, the structuremay be of a laminate of anode/luminescent layer/cathode, which arelaminated in that order. In addition to such a structure, otherstructures such as anode/hole-injection layer/luminescent layer/cathodeand anode/hole-injection layer/luminescent layer/electron transportlayer/anode may be allowable. Furthermore, instead of such a distinctlydivided laminate structure, the structure may be provided as a compositeor mixture, where the layers are hardly distinguished from each other.In the following description, all kinds of these structures will beincluded in the term of an EL layer.

In the above configuration of the light emitting device, the laminationlayer is provided on the principal surface of the plastic substrate topermit the substrate to be prevented deterioration with the transmissionof oxygen or moisture content. Furthermore, the flexible substratestructure can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional diagram that illustrates the pixelstructure of the light emitting device of the present invention, inwhich the lamination layer is formed on the substrate;

FIG. 2 is a vertical cross sectional diagram that illustrates the pixelstructure of the light emitting device of the present invention, inwhich the lamination layer is formed on the substrate;

FIG. 3 is a top view for illustrating the configuration of the lightemitting device of the present invention;

FIG. 4 is a top view for illustrating the detailed configuration of thepixel portion of the light emitting device of the present invention;

FIG. 5 is a top view for illustrating the detailed configuration of theinput terminal of the light emitting device of the present invention;

FIG. 6 is a top view for illustrating the detailed configuration of theinput terminal of the light emitting device of the present invention;

FIG. 7 is a vertical cross sectional diagram for illustrating thedetailed configuration of the input terminal of the light emittingdevice of the present invention;

FIG. 8 is a vertical cross sectional diagram for illustrating thedetailed configuration of the input terminal of the light emittingdevice of the present invention;

FIGS. 9A-9E are vertical cross sectional diagrams for illustrating theprocess for manufacturing the light emitting device of the presentinvention;

FIG. 10 is a vertical cross sectional diagram for illustrating thedetailed configuration of the pixel of the light emitting device of thepresent invention.

FIG. 11 is a vertical cross sectional diagram for illustrating theconfiguration of the light emitting device of the present invention:

FIG. 12 is a perspective view for illustrating an exemplifiedconfiguration of the light emitting device of the present invention;

FIG. 13 is a top view for illustrating the detailed configuration of thepixel portion of the light emitting device of the present invention;

FIG. 14 is a vertical cross sectional diagram for illustrating thedetailed configuration of the pixel portion of the light emitting deviceof the present invention;

FIG. 15 is a vertical cross sectional diagram for illustrating thedetailed configuration of the pixel portion of the light emitting deviceof the present invention;

FIG. 16 is a vertical cross sectional diagram for illustrating thedetailed configuration of the pixel portion of the light emitting deviceof the present invention;

FIG. 17 is a diagram that indicates one embodiment of the manufacturingdevice adapted to the formation of the lamination layer of the presentinvention on the flexible plastic substrate;

FIGS. 18A and 18B are cross sectional diagrams for illustrating thedetails of the lamination layer of the present invention;

FIGS. 19A and 19B are cross sectional diagrams for illustrating thedetails of the lamination layer of the present invention; and

FIGS. 20A-20E are diagrams that illustrates the applications of thelight-emitting device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, we will describe preferred embodiments of the presentinvention in detail with reference to the attached drawings.

As a plastic substrate to be used in the present invention, polyethersulphone, polyallylate, polyimide, polyamide, acrylic resin, epoxyresin, polyethylene terephthalate, polyethylene naphthalate, orpolycarbonate may be applied. In the following embodiments, therefore,one of these plastic substrates can be appropriately selected.

One of the main structural components of the invention is a laminationlayer comprised of a unit or a plurality of units, where each unit isprovided as a laminate structure of a metal layer and an organic layer.The lamination layer is formed on the whole principal surface of aplastic substrate on which light emitting elements are formed. Amaterial that forms the metal layer is pure aluminum, or alternativelyit may be aluminum added with 0.1 to 5% by weight of an impurityselected from scandium, titanium, niobium, silicon, and copper. Thereason of adding these impurities is to improve the stability ofaluminum and to prevent aluminum spike and migration. For providing thelaminate with flexibility, each layer has a thickness of 10 to 100 nmand is prepared by a magnetron spattering method or a vacuum depositionmethod.

A material for forming the organic compound layer may be selected fromheat-curing or photo-curing acryl compounds including methylesteracrylate, ethylester acrylate, butylester acrylate, and2-ethylhexylester acrylate; and heat-curing or photo-curing acryl,polyimide, polyamide, urethane, epoxy, epoxyamine, cyanoacrylate,polyethylene-imine, and butadiene resin materials. The thickness of theorganic compound layer is in the range of 0.1 to 10 μm. In the aboveplastic substrate, a filler is contaminated. Thus, when the surface ofthe plastic substrate has asperities with heights of several micrometersto several tens micrometers, such an uneven surface can be flattened bythe organic compound flattens.

The order of laminating the metal layer and the organic compound is notlimited. They may be laminated in the order of the metal layer to theorganic compound layer from the plastic substrate side or in the reverseorder thereof. The resulting laminate structure is provided as one unit,and then a layer product is prepared using one unit or more units.However, the number of the units may be appropriately selected forattaining the purpose of preventing the diffusion of oxygen or moisturecontent. That is, the metal layer is laminated for making the laminationlayer so as to have a thickness substantially equal to the thicknessenough to prevent the diffusion of oxygen or moisture content. In theconfiguration of the lamination layer of the present invention, thethickness of the metal layer per layer (i.e., the thickness of thealuminum film) is defined such that it does not prevent the flexibilityof the plastic substrate. In addition, it should be the thickness thatdoes not cause any damage such as cracking at the time of bending theplastic substrate. Therefore, it is designed such that a plurality ofthin metal layers is laminated. Each organic compound layer insertedbetween the layers exerts a function of relaxing the stress thereof.

FIGS. 18A and 18B are diagrams that illustrates a detailed configurationof the lamination layer. On a plastic substrate 101 to be applied in alight emitting device of the present invention, a metal layer 11 and anorganic compound layer 12 are laminated one after another to form alamination layer 10. Then, the resulting laminate structure is providedas a unit. A lamination layer comprised of one unit or a plurality ofunits is formed on a principal surface of the plastic substrate toprevent the diffusion of oxygen or moisture content from the substrateside. In addition, the laminated product is able to prevent thegeneration of oligomer on the surface of the plastic substrate as asynergistic effect. FIG. 18(B) is another configuration of thelamination layer, by which the interaction between the metal layer andthe organic compound layer can be prevented. A passive layer 1101 may beformed on the metal layer 11 by oxidizing or nitriding the metal layer11 to stabilize the surface of the metal layer 11. In the case ofaluminum as a metal layer, aluminum oxide or aluminum nitride is formed.For instance, it becomes possible to prevent the metal layer fromcorrosion damage when a material containing an amino complex or the likeis used in the organic compound layer.

In the case of forming a metal layer of 10 to 100 nm in thickness, asshown in FIG. 19A, a hole 1801 may be undesirably formed in the metallayer 11. If such a hole 1801 is formed in the metal layer 11, oxygen ormoisture content 1802 tends to permeate through the hole 1801. In thecase of forming the metal layer 11 with aluminum, however, an oxidationreaction is initiated at that portion even though the moisture content1802 is dispersed therein. As a result, as shown in FIG. 19(B), alumina1803 can be formed in the hole 1801 to seal the hole 1801. Forpositively initiating such a reaction, it is preferable to conduct aheat treatment, preferably a water vapor treatment after the formationof the laminated product.

FIG. 17 is a diagram that illustrates an example of a manufacturingdevice that allows a continuous production of a laminated productcomprised of a metal layer and an organic resin layer on a flexibleplastic substrate. The manufacturing device is configured as follows.That is, a plastic substrate is placed in a feed chamber 501. Longlengths of plastic substrate is fed without break between a cylindricalcan 506 around which long lengths of plastic substrate is wound andanother cylindrical can 507 placed in a winding chamber 502. During thisperiod, the metal layer and the organic compound layer are formed.Furthermore, there is a film-forming chamber 503 for the formation of ametal layer and a film-forming chamber 505 for the formation of anorganic compound layer between the feed chamber 501 and winding chamber502.

The feed chamber 501 and the film-forming chamber 503 for the metallayer are equipped with exhaust means 508, 509, respectively, allowingto maintain a reduced pressure state. An intermediate chamber 504 isformed between the film-forming chamber 503 for the metal layer and thefilm-forming chamber 505 for the organic compound layer to adjust apressure difference. In the case of forming a metal film in thefilm-forming chamber 503 using a magnetron spattering method, agas-inducing means 512, a target 510, an electric source 511, and so onare provided. On the other hand, the formation of an organic compoundlayer may be performed using a splay method, an application method, adrug-solution dropping method, and so on. In FIG. 17, the film-formingchamber 505 for the organic compound layer comprises an applicationmeans 513 for applying an organic compound medium, a drying means 514such as a halogen lamp or a sheath heater, and an exhaust duct 515.Consequently, the manufacturing device shown in FIG. 17 allows theformation of the lamination layer having the above configuration on theplastic substrate. For forming a lamination layer having a plurality ofthe above units, the process of forming the metal layer and the organiccompound layer may be repeated as many as the number of units.

Hereinafter, we will describe the preferred embodiments of the presentinvention with reference to the attached drawings, where they arecommonly comprised of the above plastic substrate and the laminatedproduct on the main surface of the plastic substrate.

Embodiment 1

In this embodiment, a light emitting device is of a simple matrix type,in which light emitting elements are arranged in a matrix form toconstitute a display screen. In this embodiment, we will describe anembodiment of sealing structure for protecting the light emittingelements from external contaminations such as oxygen and water vapor.

FIG. 3 is a top view for illustrating the configuration of the sealingstructure. As shown in the figure, a pixel portion 102 is formed, wherelight emitting elements are arranged in a matrix form on a substrate101. The pixel portion 102 includes a first wiring 105 in a stripe formextending in the X direction and a second wiring 106 in a stripe formextending in the Y direction. A first electrode 107 of the lightemitting element is electrically connected to the second wiring 106. Thestripe-formed first wiring 105 in the X direction and the stripe-formedsecond wiring 106 in the Y direction form their respective signal inputterminals 103, 104 on the ends of the substrate 101, respectively. Apartition wall layer 109 is formed on the inside of the substrate 101such that it is located some distance from the end of the substrate 101.An inorganic compound layer 108 is formed over the structural componentson the substrate 101 except of the signal input terminals 103, 104.

In the pixel portion 102, the area surrounded by a dotted line anddenoted by the alphabet A in FIG. 3 (an A region) is shown in FIG. 4 inmore detail. In addition, the signal input terminals 103, 104 surroundedby dotted lines and denoted by B and C (B and C regions) are shown inFIG. 5 and FIG. 6 in more detail, respectively.

In FIG. 4 that shows the details of the A region, the stripe-shapedfirst wiring 105 extending in the X direction and the stripe-shapedsecond wiring 106 extending in the Y direction are crossed each otherthrough a partition wall layer (not shown). The light emitting elementis formed on a portion where the first electrode 107 provided so as tobe fit to an opening of the partition wall layer and the first wiring105 are overlapped each other. An electroluminescent (EL) layer 110containing a luminescent material is formed between the first electrode107 and the first wiring 105.

Vertical cross sectional diagrams taken along the lines A-A′ and B-B′ ofFIG. 4 are shown in FIG. 1 and FIG. 2, respectively. In FIG. 1 which isthe cross sectional view along the line A-A′ of FIG. 4, on the principalsurface of the substrate 101, there is provided a lamination layer 10comprised of a plurality of units, each of which consists of a laminatestructure constructed of a metal layer 11 and an organic compound layer12. Alternatively, the lamination layer 10 may be comprised of alaminate structure constructed of one metal layer 11 and one organiccompound layer 12. Light-emitting elements 100 are formed on thelamination layer 10 through an intermediate layer 13. The light-emittinglayer 100 is covered with the inorganic compound layer 108 to preventthe light-emitting layer 100 from the erosive action of oxygen ormoisture content. Such a configuration can be also found in FIG. 2 whichis the vertical cross sectional view along the line B-B′ of FIG. 4.

The light emitting element 100 is constructed such that anelectroluminescent (EL) layer 110 is sandwiched between a firstelectrode 107 and a second electrode 14. For functioning the secondelectrode 14 as an anode, a conductive material having a work functionof 4 eV or more, such as indium tin oxide (ITO, indium oxide mixed withtin oxide), zinc oxide, indium zinc oxide (IZO, indium oxide mixed withzinc oxide), titanium nitride, or tungsten nitride is used. In addition,for functioning as a cathode, a conductive material having a workfunction of 4 eV or less is selected, and alloy or chemical compoundmaterial containing alkali earth metal or alkali metals such as AlLi orMgAg may be applied.

The EL layer 100 is prepared using a luminescent material and aelectron-injection transport material containing an organic compound oran inorganic compound. Also, the EL layer 100 may be constructed of oneor a plurality of layers selected from lower molecular organiccompounds, intermediate molecular organic compounds, and polymer organiccompounds on the basis of their number of molecules, and may be combinedwith a electron-injection transport or hole-injection transportinorganic compound. Furthermore, the term “intermediate molecularcompound” means an organic compound having no sublimate property andhaving a molecular weight of 20 or less, or having a linked molecularlength of 10 μm or less.

The luminescent material may be a metal complex such astris-8-quinolinolate aluminum complex or bis-(benzoquinolinorate)beryllium complex, phenyl anthracene derivative, tetra-aryl diaminederivative, or distyril benzene derivative may be used as a lowmolecular organic compound, and using the selected compound as a hostmaterial, coumarin derivative, DCM, quinacridon, rubrene, or the likemay be need. Alternatively, it may be selected from other well-knownmaterials. In addition, the macromolecular organic compound may beselected from polyparaphenylene vinylenes, polyparaphenylene,polythiophenes, polyfluorenes, and so on. Concretely, it may be selectedfrom poly(p-phenylene vinylene):(PPV), poly (2,5-dialkoxy-1,4-phenyenevinylene):(RO-PPV), poly[2-(2′-ethylhexoxy)-5-methoxy-1,4-phenylenevinylene]:(MEH-PPV), poly[2-dialkoxyphenyl)-1,4-phenylene vinylene](ROPh-PPV), poly[p-phenylene]:(PPP),Poly(2,5-dialkoxy-1,4-phenylene):(RO-PPP),poly(2,5-dihexoxy-1,4-phenylene), polythiophene:(PT),poly(3-alkylthiophene):(PAT), poly(3-hexylthiophene):(PHT), poly(3-cyclohexylthiophene):(PCHT),poly(3-cyclohexyl-4-methylthiophene):(PCHMT),poly(3,4-dicyclohexylthiophene):(PDCHT),poly[3-(4octylphenyl)-thiophene]:(POPT),poly[3-(4-octylphenyl)-2,2-bithiophene]:(PTOPT), polyfluorene:(PF),poly(9,9-dialkylfluorene):(PDAF), poly(9,9-dioctylfluorene):(PDOF), andso on.

The electron-injection transport layer may be made of an inorganiccompound material selected from diamond-like carbon (DLC), Si, Ge, andoxides or nitrides thereof, optionally doped with P, B, N, or the likein an appropriate manner.

Furthermore, it may be oxides, nitrides or fluorides of alkali metals oralkali earth metal or compounds or alloys of these metals with one of atleast Zn, Sn, V, Ru, Sm, and In.

The materials described above are taken as examples. Each of functionallayers such as a hole-injection transport layer, a hole-transport layer,a electron-transport layer, a luminescent layer, a electron-blockinglayer, and a hole-blocking layer can be prepared using these materialsand a light-emitting element can be prepared by laminating the resultinglayers. In addition, a composite layer or a mixed junction may be formedby combining these layers.

In FIG. 1 and FIG. 2, a reflector 15 is formed between the secondelectrode 14 and the partition wall layer 109 and the side walls ofwhich are exposed is made of a metal material having a high reflectivityas typified by aluminum. The reflector 15 is provided for preventing adecrease in external quantum efficiency the light emitted from the ELlayer waveguide light by a multi-path reflection between the firstelectrode 107 and the second electrode 14 to lead to from becoming. Theprinciple of such a phenomenon is schematically illustrated in FIG. 10.As shown in the figure, the reflector 15 acts effectively when the light1002 is multiply reflected between the first electrode 107 and thesecond electrode 14 and becomes waveguide light in addition to light1001 emitted from the EL layer 110 to the outside. The angle θ of thereflection surface of the reflector 15 may be in the range of about 30°to 75°, preferably 45° with respect to the principal surface of thesubstrate or the surface of the second electrode.

In FIG. 1, the stripe-shaped second wiring 106 extending in the Ydirection is electrically contact with the first electrode 107 andextends to the partition wall layer 109. The second wiring 106 may be aconductive material such as aluminum, more preferably may be formedusing a shadow mask with a vacuum deposition method.

In FIG. 5 showing the details of the B region, there is illustrated thestructure of the signal input terminal end and the vicinity thereof ofthe first wiring 105 extending in the X direction. Furthermore, avertical cross sectional view along the line C-C′ in FIG. 5 is shown inFIG. 7. Therefore, these portions will be described hereinafter withreference to both figures.

The signal input terminal 103 is formed on the same layer as that of thefirst wiring 105. That is, it is formed as a laminate of the secondelectrode 14 and the reflector 15. In addition, the signal inputterminal 103 is designed such that trances thereof are allowed to beconnected to a flexible print circuit (FPC) at the end of the plasticsubstrate 101 at a predetermined pitch. Even though the inorganicinsulating layer 108 formed on the whole surface, a part of such a layer108 corresponding to the signal input terminal 103 is removed so thatthe first wiring 105 is exposed. That is, excepting such a portion, theinorganic insulating layer 108 is formed so as to cover the side surfaceof the lamination layer 10 to increase the air-tightness to prevent theentry of oxygen and moisture content from the outside.

In FIG. 6 showing the details of the C region, there is illustrated thestructure of the signal input terminal end and the vicinity thereof ofthe second wiring 106 extending in the Y direction. Furthermore, avertical cross sectional view along the line D-D′ in FIG. 6 is shown inFIG. 8. Therefore, these portions will be described hereinafter withreference to both figures.

The signal input terminal 104 is formed of the same material as that ofthe first wiring 105. That is, it is formed of a laminate of the secondelectrode 14 and the reflector 15. In addition, the signal inputterminal 104 is electrically connected to the second wiring 106 on theoutside of the partition wall layer 109. Even though the inorganicinsulating layer 108 is formed on the whole surface, a part of such alayer 108 corresponding to the signal input terminal 104 is removed sothat the surface of the second electrode 14 is exposed. That is,excepting such a portion, the inorganic insulating layer 108 is formedso as to cover the end and side surfaces of the substrate 101 to preventthe entry of oxygen and moisture content from the outside. In FIG. 5 andFIG. 6, the configuration of the light emitting element 100 is similarto one described above, so that explanations thereof will be omitted.

Consequently, as described above, a light emitting device having asimple matrix type of pixel portion constructed of light emittingelements 100, first wiring 105, second wiring 106, and terminals 103,104 is fabricated. In the following description, furthermore, we willdescribe the process for manufacturing the light emitting element 100 indetail with reference to FIG. 9.

In FIG. 9A, an aluminum layer of 10 to 100 nm in thickness is formed asa metal layer 11, and a polyimide layer of 0.1 to 10 μm in thickness isformed as an organic compound layer 12, such that these layers arelaminated one after another to form a lamination layer 10 on a plasticsubstrate 101. An intermediate layer 13 is formed as a silicon nitridefilm of 50 to 200 nm in thickness by a high-frequency magnetronspattering method using silicon as a target without the addition ofhydrogen.

Next, as shown in FIG. 9B, a titanium nitride film of 100 to 500 nm inthickness is formed as a second electrode 14 and an aluminum film of 100to 1000 nm in thickness is formed as a reflector 15 thereon using amagnetron spattering method. Furthermore, using a photosensitive organicresin material such as polyimide or acryl, a partition layer 109 havingan opening pattern corresponding to the position of a pixel is formed soas to have a thickness of 0.5 to 5 μm. As the photosensitive organicresin material is used, the side wall of the opening is sloped. Inaddition, each of the apical and bottom end portions of the opening isformed so as to have a gentle curvature.

Using the partition layer 109 as a mask, an aluminum film that forms areflector 15 is etched with a dry etching as shown in FIG. 9C. As anetching gas, a chlorine gas such as BCl₃ or Cl₃ is used. The etching isperformed while moving the end of the partition wall layer 109 backwardto etch the aluminum of the reflector 15 such that the side wall of theopening is processed so as to be slanted. That is, the surface of thereflector 15 to be exposed to the opening is sloped so as to have anangle of slope. In addition, the selective ratio to the titanium nitridefilm located on the lower side of the laminate is the higher the better.Alternatively, as shown in the figure, a part of the titanium nitridefilm may be partially etched. It is important that a smooth surface isformed without any abnormality in the shape such as a protrusion on theside wall.

It is preferable to selectively form the EL layer 110 using a shadowmask with vacuum deposition method, an inkjet recording method, or thelike as shown in FIG. 9D. The laminating configuration and theilluminated color are arbitrary, so that the illuminated color may bechanged to red (R), green (G), or blue (B) per pixel or awhite-luminescent layer may be formed.

In an appropriate combination between a color filter and acolor-converting layer, it is preferable to have white luminescence.When the white luminescence cannot be obtained with a single pigmentincluded in a luminescent layer, a plurality of pigments is used as aluminescence center and simultaneously emitted to make white luminescentby means of an additive color mixture. In this case, a method forlaminating a luminescent layer having a different illuminated color, amethod for containing a plurality of luminescence centers in one or aplurality of luminescent layers, or the like can be applied. Withrespect to the method for obtaining white luminescence, there are twomethods. One is a method by laminating luminescent layers thatrespectively emit three primary colors, red (R), green (G), and blue(B), and performing an additive color mixture. The other is a methodutilizing the relationship of two additive complementary colors. In thecase of using additive complementary colors, a combination of blue andyellow or cyan and yellow are known. In particular, it is consideredthat the latter is advantageous because of utilizing a luminescent at ahigh wavelength region with a comparatively high visual sensitivity.

An example of the use of a low molecular organic light-emitting mediumfor the EL layer 110 is a laminate structure in which aelectron-injection transport layer, a red luminescent layer, a greenluminescent layer, a hole-transport layer, and a blue luminescent layerare laminated on a second electrode 14 one after another. Concretely,when the hole-transport layer is prepared using 1,2,4-triazolederivative (p-EtTAZ) and is provided with a film thickness of 3 nm, theamount of holes passing through the p-EtTAZ layer increases and holesare also injected into aluminum tris (8-hydroxyquinoline) (Alq3) used asa green luminescent layer, allowing luminescence. This kind of thestructure acts as a blue luminescent layer such that cyan luminescencecan be obtained as a mixture of blue luminescence from TPD and greenluminescence from Alq3. In addition, for realizing white luminescence byadding red into the cyan luminescence, a red-luminescent pigment may bedoped in either Alq3 or TPD to provide a red luminescent layer. The redluminescent pigment may be Nile Red or the like.

As another configuration of the EL layer 110, from the second electrode14, a electron-injection transport layer, a electron transport layer, aluminescent layer, a hole transport layer, and a hole-injectiontransport layer may be laminated one after another. In this case, anappropriate combination of the materials include a electron-injectiontransport layer made of Alq3 of 15 nm in thickness and a electrontransport layer made of a phenyl anthracene derivative of 20 nm inthickness. In this case, furthermore, a luminescent layer is constructedof: a first luminescent layer of 25 nm in thickness prepared by mixingtetra-aryl benzine derivative and a phenyl anthracene derivative at avolume ratio of 1:3 with the addition of 3% by volume of styryl aminederivative; and a second luminescent layer of 40 nm in thicknessprepared by mixing tetra-aryl benzine derivative and10,10′-bis[2-biphenylil]-9,9′-bianthryl (phenylanthracene derivative) ata volume ratio of 1:3 with the addition of 3% by weight of naphthacenederivative. Furthermore, a hole transport layer of 20 nm in thickness isprepared from N,N,N′,N′-tetrakis-(3-biphenyl-1-il)benzeidine(tetra-arylbenzidine derivative) and a hole injection layer of 30 nm in thicknessis prepared from N,N′-diphenyl-N,N′-bis[N-phenyl-N-4-tolyl(4-aminophenyl)] benzidine.

In the above structure, an inorganic electron-injection transport layermay be used as the above electron-injection transport layer. Inaddition, as the above inorganic electron transport layer, n-typediamond-like carbon (DLC) may be used. The n-type DLC film can beobtained by appropriately doping phosphorus or the like into DLC.Alternatively, the inorganic electron transport layer may be preparedfrom one oxide selected from alkali metal elements, alkali earth metalelements, on lanthanoide elements and one or more of inorganic materialsselected from Zn, Sn, V, Ru, Sm, and In.

After that, as shown in FIG. 9E, a first electrode 107 is formed from analuminum film containing 5 to 50 nm of lithium. In addition, a secondwiring 106 is formed of aluminum on the partition wall layer 109 using avacuum deposition method. Subsequently, a silicon nitride film is formedas an inorganic insulating layer by a high-frequency magnetronspattering method using silicon as a target, resulting in a pixelstructure illustrated in FIG. 1.

Referring now to FIG. 11, there is shown the configuration of a lightemitting device attached with a sealing plastic substrate 201 and a FPCas one of the preferred embodiments of the present invention. A sealingplastic substrate 201 is fixed on a plastic substrate 101 (on whichlight emitting elements 100 are formed) by means of a resin material 202such as a urethane resin, an epoxy resin, or a silicon resin. Also, aFPC is fixed on a signal input terminal 103 by fixing together by meansof an anisotropic conductive adhesive 204 so as to be electricallyconnected to each other. Likewise, a signal input terminal 104 is alsoconnected to the FPC. Each of the light emitting elements 100 iscompletely surrounded by a lamination layer 10 and an inorganicinsulating layer 108 to form a sealed structure independently from thesealing plastic substrate 201 and the resin material 202. Furthermore,for increasing the stability of the resulting laminated structure to theatmospheric conditions including humidity and temperature, it is alsopossible to form another sealing film or a protective film on the outersurface of the plastic substrate.

FIG. 12 is a diagram that illustrates the external configuration of alight emitting device using the plastic substrate prepared as describedabove. Just as with FIG. 11, a pixel portion 102, a FPC 203, and asealing plastic substrate 201 are formed on a plastic substrate 101. Forsurface protection and heat dissipation, a layer represented byAl_(x)N_(y) (or a layer represented by Al₂O₃) may be formed on one sideor both sides of each of the plastic substrate 101 and the sealingplastic substrate 201. In addition, a FPC 203 forms a connection to anexternal circuit. Here, only the FPC 203 is illustrated in this figure,but a print wiring board (PWB) may be attached on the FPC 203. Inaddition, but not shown in the figure, an IC chip having a memory, aCPU, a controller, a D/A converter, and so on may be mounted by means ofCOG(chip on grass)method, a tape automated boding (TAB) method or awiring-bonding method. Furthermore, the IC chip may be mounted such thatit is fixed between the plastic substrate 101 and the sealing plasticsubstrate 201.

Consequently, a simple matrix type of light emitting device having aplastic substrate capable of preventing the substrate from deteriorationwith the transmission of oxygen or moisture content can be obtained. Itis understood that, the present invention is not limited to the aboveembodiment and various kinds of modifications or changes may be allowedwithin the scope of the present invention.

Embodiment 2

In this embodiment, a light-emitting device is in the type of an activematrix in which a light emitting element and a TFT for controlling thelight emitting element are arranged on each pixel to drive. In thisembodiment, we will describe an embodiment of sealing structure forpreventing the light emitting elements and TFTs from externalcontaminations such as oxygen and water vapor.

FIG. 13 is a top view for illustrating a pixel structure of the lightemitting device, showing an exemplified configuration thereof in which aTFT and a light emitting element are mounted. FIG. 14 is a verticalcross sectional view along the line E-E′ in FIG. 13. Therefore, thepresent embodiment will be described with reference to these figures.Furthermore, in FIG. 13, the upper layers on a second electrode (i.e., apartition wall layer, an EL layer, a first electrode, and an inorganiccompound layer) are omitted for a simplification of the drawing.

As shown in the figure, a lamination layer 10 comprised of a metal layer11 and an organic compound layer 12 is formed on the principal surfaceof a plastic substrate 301. On the lamination layer 10, an intermediatelayer 302 is formed as a combination of the respective coating films ofsilicon nitride, oxidized silicon nitride, silicon oxide, and so on. Apreferable configuration of the intermediate layer 302 is a laminatecomprised of a silicon nitride film formed by a high-frequency magnetronspattering method using silicon as a target and an oxidized siliconnitride film formed on the silicon nitride film by a plasma CVD method.

In a pixel, three TFTs are mounted. A TFT 401 is a selecting TFT for anon-off operation depending on a timing of input of an image signal intothe light emitting element, a TFT 402 is an erasing TFT for terminatingthe emission of light from the light emitting element, and a TFT 403 isa driving TFT for driving the light emitting element. Preferably, theTFT 403 is of a p-channel type when a second electrode 310 a of thelight emitting element 100 is provided as an anode, or of an n-channeltype when it is provided as a cathode.

The configuration of the TFT is illustrated in FIG. 14. In this figure,there is shown a cross sectional view of the TFT 403 as an example. Asshown in the figure, the TFT 403 comprises a semiconductor film 303 onwhich a source or drain region 304 and a channel-forming region 305 areformed, a gate insulating film 306, a gate electrode 307, and so on.Furthermore, a low concentration drain region may be formed on thesemiconductor film 303 if required and the structure thereof is notlimited.

Furthermore, a protective film 308 made of silicon nitride or oxidizedsilicon nitride, and a flattening film 309 made of a photosensitiveorganic resin material are formed on the gate electrode 307. Thephotosensitive organic resin material may be a polyimide resin, an acrylresin, or the like. A contact hole extending to the source or drainregion 304 is formed such that an opening passing through the protectivefilm 308 and the gate insulating film 306 are formed by a dry etchingmethod and another opening having a diameter lager than that of theabove opening is formed in the flattening film 309.

On the flattening film, a second electrode of the light emitting elementand various kinds of wiring are formed by laminating a titanium nitridefilm 310 and an aluminum film 311. In the light-emitting element, thetitanium nitride film 310 a forms a second electrode 310 a and thealuminum film 311 forms a reflector 311 a. The second electrode 310 aand the reflector 311 a are combined with a partition layer 312 just asin the case of Embodiment 1. In addition, the titanium nitride film 310is formed in a thickness of 50 to 100 nm, and the aluminum film 311 isformed in a thickness of 100 to 2000 nm. On such a lamination layer, itis possible to form power source line (310 b/311 b) and image signalline (310 c/311 c) in addition to the electrode of the light emittingelement 100.

Furthermore, an EL layer 110, a first electrode 107, and an inorganicinsulating layer 108 are configured just as in the case of Embodiment 1,so that a light emitting device in which a pixel is formed with thelight emitting element 100 connected to the TFT 403. As a matter ofcourse, the pixel structure described in this embodiment is onlyprovided as one of preferred examples. Therefore, the pixel structure ofthe present invention is not limited to such a structure and anotherpixel structure may be applied in the present invention.

FIG. 15 shows an example of a light emitting device in which an activematrix type of pixel structure is constructed of a reverse staggered (orbottom gate) type TFT. In this case, the TFT 403 of FIG. 14 can bedirectly replaced with the reverse staggered type TFT 403′ withoutchanging other structural components. On an intermediate layer 302, agate electrode 307, a gate insulating film 306, a semiconductor film 303containing a source or drain region 304 and a channel forming region305, and a protecting film 308 are formed in that order. Otherstructural components are configured just as in the case of FIG. 14, sothat the explanations thereof will be omitted.

In FIG. 16, there is shown an example in which an active matrix type ofpixel is formed of an organic TFT using an organic semiconductor in achannel forming region. In addition, a lamination layer 10, anintermediate layer 502, a gate electrode 507, and a gate insulating film506 formed on the principal surface of a plastic substrate 501 areconfigured just as in the case of FIG. 15.

An insulating layer 505 is used as a frame for forming an organicsemiconductor in a predetermined place. An opening is formed in theinsulating layer 505 corresponding to the gate electrode 507. Theorganic semiconductor 503 can be formed by means of a printing method, asplay method, a spin coating method, an inkjet method, or the like. Theorganic semiconductor material may be preferably a δ-electron conjugatedpolymer material in which the carbon skeleton thereof is constructed ofa conjugated double bound. Concretely, a soluble polymer material suchas polythiophene, poly(3-alkylthiophene), polythiophene derivative, orthe like can be used. Other applicable organic semiconductor materialsmay be those capable of forming an organic semiconductor layer by meansof an appropriate process after the film formation from a solubleprecursor. Furthermore, the organic semiconductor materials to beprovided via precursors thereof include polythienylene vinylene,poly(2,5-thienylene vinylene), polyacetylene, polyacetylene derivative,polyallylene vinylene, and so on. At the time of converting theprecursor into the organic semiconductor, not only subjecting to aheating treatment, a reaction catalyst such as hydrogen chloride gas isadded. In addition, typical solvents useful for dissolving the solubleorganic semiconductor material include toluene, xylene, chlorobenzene,dichlorobenzen, anisole, chloroform, dichloromethane, ā-butyl lactone,butyl cellsolve, cyclohexane, NMP(N-metal-2-pyrrolidone), cyclohexanone,2-butanone, dioxane, dimethylfolmamide (DMF), or tetrahydrofuran(THF),and so on.

Souse or drain electrodes 512, 513 are contact with the organicsemiconductor 503 and function as source or drain in the organic TFT.The material that forms these wiring members is preferably a metalhaving a large work function for making ohmic contact with thesemiconductor layer because many organic semiconductor materials thattransport holes as carriers are p-type semiconductors.

After the formation of a protective film 517 and a flattening film 508,a second electrode formed of a titanium nitride 510 a, a reflectorformed of aluminum 511 a, wiring 510 b/511 b, wiring 510 c/511 c, apartition layer 512, an EL layer 110, a first electrode 107, alight-emitting element 100, and an inorganic insulating layer 108 areconfigured just as in the case of FIG. 14.

A terminal for the input of signals can be configured by the same way asthat of Embodiment 1. In other words, a sealing structure provided suchthat an inorganic compound layer covers the end surface of a laminationlayer can be realized by a light-emitting device having an active matrixtype pixel.

In the above description, the configurations of the light emittingdevices having the active matrix type of pixels using the top gate typeor bottom gate type TFT with the inorganic semiconductor and the organicTFT with the organic semiconductor have been explained. In each of thesecases, it can be used as a plastic substrate capable of preventing thetransmission of oxygen or moisture content. Furthermore, the presentinvention is not limited to the above embodiment and various kinds ofmodifications or changes may be allowed within the scope of the presentinvention.

Embodiment 3

Various kinds of electronic apparatus can be implemented with the lightemitting device of the present invention described above. Typicalelectronic apparatus includes personal digital assistants (i.e.,electronic notes, mobile computers, cellular phones, and electronicbooks and magazines), video cameras, digital cameras, cellular phones,and so on. Some of these examples are shown in FIG. 20.

In FIG. 20A, there is shown an example of a video camera implemented bythe application of the present invention. The video camera comprises amain body 3011, a display part 3012, a voice input part 3013, anoperation switch 3014, a battery unit 3015, and a viewing part 3016.Accordingly, the present invention allows the implementation of such alight-weighted video camera.

In FIG. 20B, there is shown an example of a personal digital assistant(PDA) implemented by the application of the present invention. The PDAcomprises a main body 3031, a stylus pen 3032, a display part 3033, anoperation button 3034, an external interface 3035, and so on. Thepresent invention allows the PDA to be thinned and light-weighted andimplements a weather-proof PDA.

In FIG. 20C, there is shown an example of a cellular phone implementedby the application of the present invention. The cellular phonecomprises a main body 3061, a voice output part 3062, a voice input part3063, a display part 3064, an operation switch 3065, an antenna 3066,and so on. The present invention allows the cellular phone to be thinnedand light-weighted and implements a weather-proof cellular phone.

In FIG. 20D, there is shown an example of a digital camera implementedby the application of the present invention. The digital cameracomprises a main body 3051, a display part (A) 3052, an ocular part3053, an operation switch 3054, a display part (B) 3055, a battery unit3056, and so on. The present invention allows the digital camera to bethinned and light-weighted and implements a weather-proof digitalcamera.

In FIG. 20E, there is shown an example of a digital book or magazineimplemented by the application of the present invention. The digitalbook (magazine) comprises a main body 3101, a display part (A) 3102, adisplay part (B) 3103, a recording medium 3104, an operation system3105, an antenna 3106, and so on. The present invention allows thedigital book to be thinned and light-weighted and implements aweather-proof digital book magazine.

Furthermore, these digital apparatus are a small part of theapplications of the present invention, so that the present inventioncannot be restricted by the electronic apparatus described above.

According to the present invention, therefore, a lamination layerconstructed of a metal layer and an organic compound layer can be formedon a plastic substrate, so that a light emitting device having a simplematrix or active matrix type of pixel structure that prevents thesubstrate from deterioration with the transmission of oxygen or moisturecontent can be obtained.

1. (canceled)
 2. A light emitting device comprising: a light emittingregion having a plurality of light emitting elements, each including afirst electrode, an organic compound layer formed over the firstelectrode, and a second electrode formed over the organic compoundlayer; and an inorganic insulating layer formed over the secondelectrode, wherein an end portion of the first electrode is covered witha partition wall layer, and wherein a portion of the first electrode isthinner than the end portion of the first electrode.
 3. A light emittingdevice according to claim 2, wherein the inorganic insulating layer is asilicon nitride film.
 4. A light emitting device according to claim 2,wherein the metal layer is formed of aluminum or aluminum alloy.
 5. Alight emitting device according to claim 2, wherein the first electrodehas an angle θ of a reflection surface of a reflector.
 6. A lightemitting device according to claim 2, wherein the first electrode has anangle θ of a reflection surface of a reflector, and wherein the angle θis in the range of about 30° to 75°.
 7. A light emitting devicecomprising: a light emitting region having a plurality of light emittingelements, each including a first electrode, an organic compound layerformed over the first electrode, and a second electrode formed over theorganic compound layer; an inorganic insulating layer formed over thesecond electrode; and a metal layer formed over an end portion of thefirst electrode, wherein the end portion of the first electrode iscovered with a partition wall layer, and wherein a portion of the firstelectrode is thinner than the end portion of the first electrode.
 8. Alight emitting device according to claim 7, wherein the inorganicinsulating layer is a silicon nitride film.
 9. A light emitting deviceaccording to claim 7, wherein the metal layer is formed of aluminum oraluminum alloy.
 10. A light emitting device according to claim 7,wherein the first electrode has an angle θ of a reflection surface of areflector.
 11. A light emitting device according to claim 7, wherein thefirst electrode has an angle θ of a reflection surface of a reflector,and wherein the angle θ is in the range of about 30° to 75°.
 12. A lightemitting device according to claim 7, wherein the metal layer has anangle θ of a reflection surface of a reflector.
 13. A light emittingdevice according to claim 7, wherein the metal layer has an angle θ of areflection surface of a reflector, and wherein the angle θ is in therange of about 30° to 75°.
 14. A light emitting device comprising: afirst plastic substrate; a second plastic substrate; a light emittingregion having a plurality of light emitting elements, each including afirst electrode, an organic compound layer formed over the firstelectrode, and a second electrode formed over the organic compoundlayer; and an inorganic insulating layer formed over the secondelectrode, wherein the light emitting region is formed between the firstand second plastic substrates, wherein the end portion of the firstelectrode is covered with a partition wall layer, and wherein a portionof the first electrode is thinner than the end portion of the firstelectrode.
 15. A light emitting device according to claim 14, whereinthe inorganic insulating layer is a silicon nitride film.
 16. A lightemitting device according to claim 14, wherein the first electrode hasan angle θ of a reflection surface of a reflector.
 17. A light emittingdevice according to claim 14, wherein the first electrode has an angle θof a reflection surface of a reflector, and wherein the angle θ is inthe range of about 30° to 75°.
 18. A light emitting device according toclaim 14, wherein the first and second plastic substrates are bending.